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Stanley M. Parsons - One of the best experts on this subject based on the ideXlab platform.
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Radiosynthesis and evaluation of a fluorine-18 labeled radioligand targeting Vesicular Acetylcholine Transporter
Bioorganic & medicinal chemistry letters, 2018Co-Authors: Xuyi Yue, Stanley M. Parsons, Kota Kaneshige, Zonghua Luo, Hui Liu, Joel S. PerlmutterAbstract:Abstract Vesicular Acetylcholine Transporter (VAChT) is a reliable biomarker for assessing the loss of cholinergic neurons in the brain that is associated with cognitive impairment of patients. 5-Hydrotetralin compound (±)-5-OH-VAT is potent (Ki = 4.64 ± 0.32 nM) and selective for VAChT (>1800-fold and 398-fold for σ1 and σ2 receptor, respectively) with favorable hydrophilicity (LogD = 1.78), while (−)-5-OH-VAT originally serves as the radiolabeling precursor of (−)-[18F]VAT, a promising VAChT radiotracer with a logD value of 2.56. To evaluate (−)-5-OH-[18F]VAT as a radiotracer for VAChT, we performed in vitro binding assay to determine the potency of the minus enantiomer (−)-5-OH-VAT and plus enantiomer (+)-5-OH-VAT, indicating that (−)-5-OH-VAT is a more potent VAChT enantiomer. Radiosynthesis of (−)-5-OH-[18F]VAT was explored using three strategies. (−)-5-OH-[18F]VAT was achieved with a good yield (24 ± 6%) and high molar activity (∼37 GBq/µmol, at the end of synthesis) using a microwave assisted two-step one-pot procedure that started with di-MOM protected nitro-containing precursor (−)-6. MicroPET studies in the brain of nonhuman primate (NHP) suggest that (−)-5-OH-[18F]VAT readily penetrated the blood brain barrier and specifically accumulated in the VAChT-enriched striatum with improved washout kinetics from striatum compared to [18F]VAT. Nevertheless, the lower target to non-target ratio may limit its use for in vivo measurement of the VAChT level in the brain.
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exploration of sulfur containing analogues for imaging Vesicular Acetylcholine Transporter in the brain
ChemMedChem, 2018Co-Authors: Zonghua Luo, Hongjun Jin, Joel S. Perlmutter, Kota Kaneshige, Hui Liu, Stanley M. ParsonsAbstract:Sixteen new sulfur-containing compounds targeting the Vesicular Acetylcholine Transporter (VAChT) were synthesized and assessed for in vitro binding affinities. Enantiomers (-)-(1-(3-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)piperidin-4-yl)(4-(methylthio)phenyl)methanone [(-)-8] and (-)-(4-((2-fluoroethyl)thio)phenyl)(1-(3-hydroxy-1,2,3,4-tetrahydronaph-thalen-2-yl)piperidin-4-yl)methanone [(-)-14 a] displayed high binding affinities, with respective Ki values of 1.4 and 2.2 nm for human VAChT, moderate and high selectivity for human VAChT over σ1 (≈13-fold) and σ2 receptors (>420-fold). Radiosyntheses of (-)-[11 C]8 and (-)-[18 F]14 a were achieved using conventional methods. Ex vivo autoradiography and biodistribution studies in Sprague-Dawley rats indicated that both radiotracers have the capacity to penetrate the blood-brain barrier, with high initial brain uptake at 5 min and rapid washout. The striatal region had the highest accumulation for both radiotracers. Pretreating the rats with the VAChT ligand (-)-vesamicol decreased brain uptake for both radiotracers. Pretreating the rats with the σ1 ligand YUN-122 (N-(4-benzylcyclohexyl)-2-(2-fluorophenyl)acetamide) also decreased brain uptake, suggesting these two radiotracers also bind to the σ1 receptor in vivo. The microPET study of (-)-[11 C]8 in the brain of a non-human primate showed high striatal accumulation that peaked quickly and washed out rapidly. Although preliminary results indicated these two sulfur-containing radiotracers have high binding affinities for VAChT with rapid washout kinetics from the striatum, their σ1 receptor binding properties limit their potential as radiotracers for quantifying VAChT in vivo.
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Exploration of Sulfur‐Containing Analogues for Imaging Vesicular Acetylcholine Transporter in the Brain
ChemMedChem, 2018Co-Authors: Zonghua Luo, Hongjun Jin, Joel S. Perlmutter, Kota Kaneshige, Hui Liu, Stanley M. ParsonsAbstract:Sixteen new sulfur-containing compounds targeting the Vesicular Acetylcholine Transporter (VAChT) were synthesized and assessed for in vitro binding affinities. Enantiomers (-)-(1-(3-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)piperidin-4-yl)(4-(methylthio)phenyl)methanone [(-)-8] and (-)-(4-((2-fluoroethyl)thio)phenyl)(1-(3-hydroxy-1,2,3,4-tetrahydronaph-thalen-2-yl)piperidin-4-yl)methanone [(-)-14 a] displayed high binding affinities, with respective Ki values of 1.4 and 2.2 nm for human VAChT, moderate and high selectivity for human VAChT over σ1 (≈13-fold) and σ2 receptors (>420-fold). Radiosyntheses of (-)-[11 C]8 and (-)-[18 F]14 a were achieved using conventional methods. Ex vivo autoradiography and biodistribution studies in Sprague-Dawley rats indicated that both radiotracers have the capacity to penetrate the blood-brain barrier, with high initial brain uptake at 5 min and rapid washout. The striatal region had the highest accumulation for both radiotracers. Pretreating the rats with the VAChT ligand (-)-vesamicol decreased brain uptake for both radiotracers. Pretreating the rats with the σ1 ligand YUN-122 (N-(4-benzylcyclohexyl)-2-(2-fluorophenyl)acetamide) also decreased brain uptake, suggesting these two radiotracers also bind to the σ1 receptor in vivo. The microPET study of (-)-[11 C]8 in the brain of a non-human primate showed high striatal accumulation that peaked quickly and washed out rapidly. Although preliminary results indicated these two sulfur-containing radiotracers have high binding affinities for VAChT with rapid washout kinetics from the striatum, their σ1 receptor binding properties limit their potential as radiotracers for quantifying VAChT in vivo.
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Syntheses and Radiosyntheses of Two Carbon-11 Labeled Potent and Selective Radioligands for Imaging Vesicular Acetylcholine Transporter
Molecular Imaging and Biology, 2014Co-Authors: Prashanth K. Padakanti, Stanley M. Parsons, Xiang Zhang, Joel S. Perlmutter, Junfeng Li, Zhude TuAbstract:Purpose The Vesicular Acetylcholine Transporter (VAChT) is a specific biomarker for imaging presynaptic cholinergic neurons. The syntheses and C-11 labeling of two potent enantiopure VAChT inhibitors are reported here. Procedures Two VAChT inhibitors, (±)- 2 and (±)- 6 , were successfully synthesized. A chiral HPLC column was used to resolve the enantiomers from each corresponding racemic mixture for in vitro characterization. The radiosyntheses of (−)-[^11C] 2 and (−)-[^11C] 6 from the corresponding desmethyl phenol precursor was accomplished using [^11C]methyl iodide or [^11C]methyl triflate, respectively. Results The synthesis of (−)-[^11C] 2 was accomplished with 40–50 % radiochemical yield (decay-corrected), SA > 480 GBq/μmol (EOB), and radiochemical purity >99 %. Synthesis of (−)-[^11C] 6 was accomplished with 5–10 % yield, SA > 140 GBq/μmol (EOB), and radiochemical purity >97 %. The radiosynthesis and dose formulation of each tracer was completed in 55–60 min. Conclusions Two potent enantiopure VAChT ligands were synthesized and ^11C-labeled with good radiochemical yield and specific activity.
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Syntheses and radiosyntheses of two carbon-11 labeled potent and selective radioligands for imaging Vesicular Acetylcholine Transporter.
Molecular imaging and biology, 2014Co-Authors: Prashanth K. Padakanti, Stanley M. Parsons, Xiang Zhang, Joel S. PerlmutterAbstract:Purpose The Vesicular Acetylcholine Transporter (VAChT) is a specific biomarker for imaging presynaptic cholinergic neurons. The syntheses and C-11 labeling of two potent enantiopure VAChT inhibitors are reported here.
Marco A. M. Prado - One of the best experts on this subject based on the ideXlab platform.
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reduced Vesicular Acetylcholine Transporter favors antidepressant behaviors and modulates serotonin and dopamine in female mouse brain
Behavioural Brain Research, 2017Co-Authors: Marco A. M. Prado, Vânia F. Prado, Marina Paduareis, Nayara S S Aquino, Vinicius E M Oliveira, Raphael E Szawka, Grace S. PereiraAbstract:Depression is extremely harmful to modern society. Despite its complex spectrum of symptoms, previous studies have mostly focused on the monaminergic system in search of pharmacological targets. However, other neurotransmitter systems have also been linked to the pathophysiology of depression. In this study, we provide evidence for a role of the cholinergic system in depressive-like behavior of female mice. We evaluated mice knockdown for the Vesicular Acetylcholine Transporter (VAChT KD mice), which have been previously shown to exhibit reduced cholinergic transmission. Animals were subjected to the tail suspension and marble burying tests, classical paradigms to assess depressive-like behaviors and to screen for novel antidepressant drugs. In addition, brain levels of serotonin and dopamine were measured by high performance liquid chromatography. We found that female homozygous VAChT KD mice spent less time immobile during tail suspension and buried less marbles, indicating a less depressive phenotype. These differences in behavior were reverted by central, but not peripheral, Acetylcholinesterase inhibition. Moreover, female homozygous VAChT KD mice exhibited higher levels of dopamine and serotonin in the striatum, and increased dopamine in the hippocampus. Our study thus shows a connection between depressive-like behaviors and the cholinergic system, and that the latter interacts with the monoaminergic system.
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deletion of the Vesicular Acetylcholine Transporter from pedunculopontine laterodorsal tegmental neurons modifies gait
Journal of Neurochemistry, 2017Co-Authors: Helena Janickova, Marco A. M. Prado, Kaie Rosborough, Ornela Kljakic, Monica S. Guzman, Robert Gros, Mohammed A Alonaizi, Vânia F. PradoAbstract:Postural instability and gait disturbances, common disabilities in the elderly and frequently present in Parkinson's disease (PD), have been suggested to be related to dysfunctional cholinergic signalling in the brainstem. We investigated how long-term loss of cholinergic signalling from mesopontine nuclei influence motor behaviours. We selectively eliminated the Vesicular Acetylcholine Transporter (VAChT) in pedunculopontine and laterodorsal tegmental nuclei cholinergic neurons to generate mice with selective mesopontine cholinergic deficiency (VAChTEn1-Cre-flox/flox). VAChTEn1-Cre-flox/flox mice did not show any gross health or neuromuscular abnormality on metabolic cages, wire-hang and grip-force tests. Young VAChTEn1-Cre-flox/flox mice (2-5 months-old) presented motor learning/coordination deficits on the rotarod; moved slower, and had smaller steps on the catwalk, but showed no difference in locomotor activity on the open field. Old VAChTEn1-Creflox/flox mice (13-16 months-old) showed more pronounced motor learning/balance deficits on the rotarod, and more pronounced balance deficits on the catwalk. Furthermore, old mutants moved faster than controls, but with similar step length. Additionally, old VAChT-deficient mice were hyperactive. These results suggest that dysfunction of cholinergic neurons from mesopontine nuclei, which is commonly seen in PD, has causal roles in motor functions. Prevention of mesopontine cholinergic failure may help to prevent/improve postural instability and falls in PD patients. This article is protected by copyright. All rights reserved.
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Deletion of the Vesicular Acetylcholine Transporter from pedunculopontine/laterodorsal tegmental neurons modifies gait.
Journal of neurochemistry, 2017Co-Authors: Helena Janickova, Marco A. M. Prado, Kaie Rosborough, Mohammed A. Al-onaizi, Ornela Kljakic, Monica S. Guzman, Robert Gros, Vânia F. PradoAbstract:Postural instability and gait disturbances, common disabilities in the elderly and frequently present in Parkinson's disease (PD), have been suggested to be related to dysfunctional cholinergic signalling in the brainstem. We investigated how long-term loss of cholinergic signalling from mesopontine nuclei influence motor behaviours. We selectively eliminated the Vesicular Acetylcholine Transporter (VAChT) in pedunculopontine and laterodorsal tegmental nuclei cholinergic neurons to generate mice with selective mesopontine cholinergic deficiency (VAChTEn1-Cre-flox/flox). VAChTEn1-Cre-flox/flox mice did not show any gross health or neuromuscular abnormality on metabolic cages, wire-hang and grip-force tests. Young VAChTEn1-Cre-flox/flox mice (2-5 months-old) presented motor learning/coordination deficits on the rotarod; moved slower, and had smaller steps on the catwalk, but showed no difference in locomotor activity on the open field. Old VAChTEn1-Creflox/flox mice (13-16 months-old) showed more pronounced motor learning/balance deficits on the rotarod, and more pronounced balance deficits on the catwalk. Furthermore, old mutants moved faster than controls, but with similar step length. Additionally, old VAChT-deficient mice were hyperactive. These results suggest that dysfunction of cholinergic neurons from mesopontine nuclei, which is commonly seen in PD, has causal roles in motor functions. Prevention of mesopontine cholinergic failure may help to prevent/improve postural instability and falls in PD patients. This article is protected by copyright. All rights reserved.
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Pulmonary inflammation is regulated by the levels of the Vesicular Acetylcholine Transporter.
PloS one, 2015Co-Authors: Nathalia Pinheiro, Marco A. M. Prado, Cláudia Miranda, Adenir Perini, Niels Olsen Saraiva Câmara, Soraia K.p. Costa, Maria Isabel Cardoso Alonso-vale, Luciana C. Caperuto, Iolanda F.l.c. Tibério, Milton A. MartinsAbstract:Acetylcholine (ACh) plays a crucial role in physiological responses of both the central and the peripheral nervous system. Moreover, ACh was described as an anti-inflammatory mediator involved in the suppression of exacerbated innate response and cytokine release in various organs. However, the specific contributions of endogenous release ACh for inflammatory responses in the lung are not well understood. To address this question we have used mice with reduced levels of the Vesicular Acetylcholine Transporter (VAChT), a protein required for ACh storage in secretory vesicles. VAChT deficiency induced airway inflammation with enhanced TNF-α and IL-4 content, but not IL-6, IL-13 and IL-10 quantified by ELISA. Mice with decreased levels of VAChT presented increased collagen and elastic fibers deposition in airway walls which was consistent with an increase in inflammatory cells positive to MMP-9 and TIMP-1 in the lung. In vivo lung function evaluation showed airway hyperresponsiveness to methacholine in mutant mice. The expression of nuclear factor-kappa B (p65-NF-kB) in lung of VAChT-deficient mice were higher than in wild-type mice, whereas a decreased expression of janus-kinase 2 (JAK2) was observed in the lung of mutant animals. Our findings show the first evidence that cholinergic deficiency impaired lung function and produce local inflammation. Our data supports the notion that cholinergic system modulates airway inflammation by modulation of JAK2 and NF-kB pathway. We proposed that intact cholinergic pathway is necessary to maintain the lung homeostasis.
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Abstract 422: Cardiovascular Regulation in Mice with Overexpression of the Gene of Vesicular Acetylcholine Transporter (VAChT)
Hypertension, 2014Co-Authors: Geisa C.s.v. Tezini, Marco A. M. Prado, Silvia Guatimosim, Diogo Guimarães, Mauro De Oliveira, Rubens Fazan, Helio Cesar SalgadoAbstract:It was recently developed a transgenic animal model with overexpression of cholinergic neurotransmission. This mouse, named ChAT-ChR2-EYFP, has several extra copies of the Vesicular Acetylcholine Transporter (VAChT) gene and exhibits three-fold increase in the release of Acetylcholine. However, the consequences of overexpression of VAChT protein to the cardiovascular system have not yet been characterized. Therefore, we have investigated the effects of the overexpression of the gene of VAChT on arterial pressure (AP) and heart rate (HR) as well as the autonomic cardiovascular regulation. Mice were assigned into two groups: Wild-type (WT, n=7) and ChAT-ChR2-EYFP (n=7). These animals were anesthetized (isoflurane) and implanted with probes to record AP by telemetry. After 10 days, the mice had basal AP and HR recorded continuously. Assessment of the autonomic function was conducted throughout the following approaches: 1) cardiac sympathovagal balance evaluated by HR responses to methylatropine and propranolol; 2) overall HR variability; 3) spontaneous baroreflex sensitivity by the sequence analysis. ChAT-ChR2-EYFP mice showed lower basal HR (461±8 vs. 502±14 bpm, p
Jeffrey D. Erickson - One of the best experts on this subject based on the ideXlab platform.
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Brain Vesicular Acetylcholine Transporter in human users of drugs of abuse.
Synapse (New York N.Y.), 2004Co-Authors: Deborah M. Siegal, Hélène Varoqui, Jeffrey D. Erickson, Lee Ang, Kathryn S. Kalasinsky, Frank J. Peretti, Sally S. Aiken, Dennis J. Wickham, Stephen J. KishAbstract:Limited animal data suggest that the dopaminergic neurotoxin methamphetamine is not toxic to brain (striatal) cholinergic neurons. However, we previously reported that activity of choline acetyltransferase (ChAT), the cholinergic marker synthetic enzyme, can be very low in brain of some human high-dose methamphetamine users. We measured, by quantitative immunoblotting, concentrations of a second cholinergic marker, the Vesicular Acetylcholine Transporter (VAChT), considered to be a "stable" marker of cholinergic neurons, in autopsied brain (caudate, hippocampus) of chronic users of methamphetamine and, for comparison, in brain of users of cocaine, heroin, and matched controls. Western blot analyses showed normal levels of VAChT immunoreactivity in hippocampus of all drug user groups, whereas in the dopamine-rich caudate VAChT levels were selectively elevated (+48%) in the methamphetamine group, including the three high-dose methamphetamine users who had severely reduced ChAT activity. To the extent that cholinergic neuron integrity can be inferred from VAChT concentration, our data suggest that methamphetamine does not cause loss of striatal cholinergic neurons, but might damage/downregulate brain ChAT in some high-dose users. However, the finding of increased VAChT levels suggests that brain VAChT concentration might be subject to up- and downregulation as part of a compensatory process to maintain homeostasis of neuronal cholinergic activity. This possibility should be taken into account when utilizing VAChT as a neuroimaging outcome marker for cholinergic neuron number in human studies.
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The Cytoplasmic Tail of the Vesicular Acetylcholine Transporter Contains a Synaptic Vesicle Targeting Signal
The Journal of biological chemistry, 1998Co-Authors: Hélène Varoqui, Jeffrey D. EricksonAbstract:The human homologue of the Vesicular Acetylcholine Transporter (hVAChT) and the neuronal isoform of the Vesicular monoamine Transporter (hVMAT2) are differentially targeted to two populations of regulated secretory organelles when expressed in PC12 cells. Western blot analysis of subcellular fractions from sucrose equilibrium density gradients and glycerol velocity gradients of homogenates from stably transfected cells revealed hVAChT immunoreactivity in fractions that contain synaptophysin, a marker of synaptic vesicles, while hVMAT2 immunoreactivity was confined to heavy fractions containing chromogranin B, a marker of large dense core vesicles. In cells treated with nerve growth factor, hVAChT immunoreactivity alone co-localized with synaptophysin and was abundantly expressed on synaptic vesicle clusters. Chimeras between hVMAT2 and hVAChT were utilized to identify the domain of hVAChT required for its expression on synaptic vesicles and which would shift the expression of hVMAT2 from large dense core vesicles to synaptic vesicles. Biochemical, immunocytochemical, and electron microscopic analyses revealed that a chimera in which the cytoplasmic tail of hVMAT2 was replaced with hVAChT sequences was now preferentially targeted to synaptic vesicles. In addition, hVAChT expression on synaptic vesicles was nearly abolished when the hVMAT2 cytoplasmic tail was present. Thus, structural information resides within the terminal cytoplasmic domain of VAChT, which specifically targets it to synaptic vesicles.
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DISSOCIATION OF THE Vesicular Acetylcholine Transporter DOMAINS IMPORTANT FOR HIGH-AFFINITY TRANSPORT RECOGNITION, BINDING OF VESAMICOL AND TARGETING TO SYNAPTIC VESICLES
Journal of physiology Paris, 1998Co-Authors: Hélène Varoqui, Jeffrey D. EricksonAbstract:Chimeras between the human Vesicular Acetylcholine Transporter (hVAChT) and the neuronal isoform of the human Vesicular monoamine Transporter (hVMAT2) have been constructed and stably expressed in a rat pheochromocytoma cell line (PC12) in an effort to identify cholinergic-specific domains of VAChT. Examination of the transport properties of a chimera in which the N-terminal portion (up to putative transmembrane domain II and including the lumenal glycosylated loop) of hVAChT was replaced with hVMAT2 sequences (2/V@NheI) revealed that its apparent affinity for Acetylcholine (ACh) was reduced approximately seven-fold compared to wild-type. However, the affinity of this chimera for vesamicol did not significantly differ from hVAChT. Similarly, the 2/V@NheI chimera retained its preferential targeting to the small synaptic-like vesicles found in PC12 cells in agreement with our recently reported observations that the synaptic vesicle targeting domain resides in the cytoplasmic tail of VAChT.
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Active Transport of Acetylcholine by the Human Vesicular Acetylcholine Transporter
The Journal of biological chemistry, 1996Co-Authors: Hélène Varoqui, Jeffrey D. EricksonAbstract:Abstract The characteristics of ATP-dependent transport of Acetylcholine (ACh) in homogenates of pheochromocytoma (PC-12) cells stably transfected with the human Vesicular Acetylcholine Transporter (VAChT) cDNA are described. The human VAChT protein was abundantly expressed in this line and appeared as a diffuse band with a molecular mass of ∼75 kDa on Western blots. Vesicular [3H]ACh accumulation increased ∼20 times over levels attained by the endogenous rat VAChT, expressed at low levels in control PC-12 cells. The transport of [3H]ACh by human VAChT was dependent upon the addition of exogenous ATP at 37°C. Uptake was abolished by low temperature (4°C), the proton ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (2.5 µM) and bafilomycin A1 (1 µM), a specific inhibitor of the Vesicular H+-ATPase. The kinetics of [3H]ACh uptake by human VAChT were saturable, exhibiting an apparent Km of 0.97 ± 0.1 mM and Vmax of 0.58 ± 0.04 nmol/min/mg. Maximal steady-state levels of Vesicular [3H]ACh accumulation were directly proportional to the concentration of substrate present in the medium with saturation occurring at ∼4 mM. Uptake was stereospecifically inhibited by L-vesamicol with an IC50 of 14.7 ± 1.5 nM. The apparent affinity (Kd) of [3H]vesamicol for human VAChT was 4.1 ± 0.5 nM, and the Bmax was 8.9 ± 0.6 pmol/mg. The turnover (Vmax/Bmax) of the human VAChT was ∼65/min. This expression system should prove useful for the structure/function analysis of VAChT.
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Human and monkey cholinergic neurons visualized in paraffin-embedded tissues by immunoreactivity for VAChT, the Vesicular Acetylcholine Transporter.
Journal of molecular neuroscience : MN, 1995Co-Authors: Martin K.-h. Schäfer, Eberhard Weihe, Jeffrey D. Erickson, Lee E. EidenAbstract:The predicted C-terminal dodecapeptide of the human Vesicular Acetylcholine Transporter (VAChT), deduced from the unique open reading frame of the recently cloned human VAChT cDNA, was conjugated through an N-terminal cysteine to keyhole limpet hemocyanin and used as an immunogen to generate polyclonal antihuman VAChT antibodies in rabbits. The distribution of the VAChT antigen in representative regions of the cholinergic nervous system was examined and compared to that of the Acetylcholine biosynthetic enzyme choline acetyltransferase (ChAT), a specific marker for cholinergic neurons.
Robert H. Mach - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and in vitro biological evaluation of carbonyl group-containing inhibitors of Vesicular Acetylcholine Transporter.
Journal of Medicinal Chemistry, 2010Co-Authors: Simon M N Efange, Stanley M. Parsons, A. B. Khare, Krystyna Von Hohenberg, Robert H. Mach, Zhude TuAbstract:To identify selective high-affinity inhibitors of the Vesicular Acetylcholine Transporter (VAChT), we have interposed a carbonyl group between the phenyl and piperidyl groups of the prototypical VAChT ligand vesamicol and its more potent analogues benzovesamicol and 5-aminobenzovesamicol. Of 33 compounds synthesized and tested, 6 display very high affinity for VAChT (Ki, 0.25−0.66 nM) and greater than 500-fold selectivity for VAChT over σ1 and σ2 receptors. Twelve compounds have high affinity (Ki, 1.0−10 nM) and good selectivity for VAChT. Furthermore, 3 halogenated compounds, namely, trans-3-[4-(4-fluorobenzoyl)piperidinyl]-2-hydroxy-1,2,3,4-tetrahydronaphthalene (28b) (Ki = 2.7 nM, VAChT/sigma selectivity index = 70), trans-3-[4-(5-iodothienylcarbonyl)piperidinyl]-2-hydroxy-1,2,3,4-tetrahydronaphthalene (28h) (Ki = 0.66 nM, VAChT/sigma selectivity index = 294), and 5-amino-3-[4-(p-fluorobenzoyl)piperidinyl]-2-hydroxy-1,2,3,4,-tetrahydronaphthalene (30b) (Ki = 2.40 nM, VAChT/sigma selectivity index = 410...
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Hydroxylated decahydroquinolines as ligands for the Vesicular Acetylcholine Transporter: synthesis and biological evaluation.
Journal of medicinal chemistry, 1999Co-Authors: Simon M N Efange, A. B. Khare, Robert H. Mach, Stanley M. ParsonsAbstract:Analogues of the potent anticholinergic 2-(4-phenylpiperidino)cyclohexanol (vesamicol, 1) in which the cyclohexyl fragment was replaced with an N-acyl or N-alkyl trans-decahydroquinolyl moiety were synthesized and evaluated as potential ligands for the Vesicular Acetylcholine Transporter (VAChT). The binding of compounds, such as 18, 20, and 21, was both stereospecific and of comparable magnitude to that of the closely related vesamicol analogue 2,3-trans-4a,8a-trans-3-hydroxy-2-(4-phenylpiperidino)-1,2,3,4,5,6,7,8-decahydronaphthalene (6) which displays subnanomolar affinity for this Transporter. However, these compounds also demonstrated high affinities for σ1 and σ2 receptors and thus failed to show significantly improved selectivity over previously reported vesamicol analogues.
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p 18f fluorobenzyl spirotrozamicol 18f spiro fbt synthesis and biological evaluation of a high affinity ligand for the Vesicular Acetylcholine Transporter vacht
Nuclear Medicine and Biology, 1999Co-Authors: Simon M N Efange, A. B. Khare, Michael A. Nader, Richard L. Ehrenkaufer, Cynthia R. Smith, Thomas E. Morton, Robert H. MachAbstract:Abstract (+)-1′-[4-Hydroxy-1-(4-fluorobenzyl)piperidin-3-yl]spiro[1H-indene-1,4′-piperidine] {(+)-Spiro-FBT}, a high-affinity Vesicular Acetylcholine Transporter ligand, was labeled with fluorine-18, and evaluated in the rat and monkey. In the rat brain, (+)-[ 18 F]Spiro-FBT accumulated preferentially in the striatum, hippocampus, and cortex, brains regions containing high-to-moderate densities of cholinergic terminals. However, due to rapid metabolism, no preferential accumulation of the radiotracer was observed in corresponding regions of the monkey brain. Consequently, rapid metabolism renders (+)-[ 18 F]Spiro-FBT unsuitable for studying cholinergic function with positron emission tomography.
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(+)-p-([18F]fluorobenzyl)spirotrozamicol {(+)-[18F]Spiro-FBT}: synthesis and biological evaluation of a high-affinity ligand for the Vesicular Acetylcholine Transporter (VAChT)
Nuclear medicine and biology, 1999Co-Authors: Simon M N Efange, A. B. Khare, Michael A. Nader, Richard L. Ehrenkaufer, Cynthia R. Smith, Thomas E. Morton, Robert H. MachAbstract:Abstract (+)-1′-[4-Hydroxy-1-(4-fluorobenzyl)piperidin-3-yl]spiro[1H-indene-1,4′-piperidine] {(+)-Spiro-FBT}, a high-affinity Vesicular Acetylcholine Transporter ligand, was labeled with fluorine-18, and evaluated in the rat and monkey. In the rat brain, (+)-[ 18 F]Spiro-FBT accumulated preferentially in the striatum, hippocampus, and cortex, brains regions containing high-to-moderate densities of cholinergic terminals. However, due to rapid metabolism, no preferential accumulation of the radiotracer was observed in corresponding regions of the monkey brain. Consequently, rapid metabolism renders (+)-[ 18 F]Spiro-FBT unsuitable for studying cholinergic function with positron emission tomography.
Vânia F. Prado - One of the best experts on this subject based on the ideXlab platform.
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reduced Vesicular Acetylcholine Transporter favors antidepressant behaviors and modulates serotonin and dopamine in female mouse brain
Behavioural Brain Research, 2017Co-Authors: Marco A. M. Prado, Vânia F. Prado, Marina Paduareis, Nayara S S Aquino, Vinicius E M Oliveira, Raphael E Szawka, Grace S. PereiraAbstract:Depression is extremely harmful to modern society. Despite its complex spectrum of symptoms, previous studies have mostly focused on the monaminergic system in search of pharmacological targets. However, other neurotransmitter systems have also been linked to the pathophysiology of depression. In this study, we provide evidence for a role of the cholinergic system in depressive-like behavior of female mice. We evaluated mice knockdown for the Vesicular Acetylcholine Transporter (VAChT KD mice), which have been previously shown to exhibit reduced cholinergic transmission. Animals were subjected to the tail suspension and marble burying tests, classical paradigms to assess depressive-like behaviors and to screen for novel antidepressant drugs. In addition, brain levels of serotonin and dopamine were measured by high performance liquid chromatography. We found that female homozygous VAChT KD mice spent less time immobile during tail suspension and buried less marbles, indicating a less depressive phenotype. These differences in behavior were reverted by central, but not peripheral, Acetylcholinesterase inhibition. Moreover, female homozygous VAChT KD mice exhibited higher levels of dopamine and serotonin in the striatum, and increased dopamine in the hippocampus. Our study thus shows a connection between depressive-like behaviors and the cholinergic system, and that the latter interacts with the monoaminergic system.
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deletion of the Vesicular Acetylcholine Transporter from pedunculopontine laterodorsal tegmental neurons modifies gait
Journal of Neurochemistry, 2017Co-Authors: Helena Janickova, Marco A. M. Prado, Kaie Rosborough, Ornela Kljakic, Monica S. Guzman, Robert Gros, Mohammed A Alonaizi, Vânia F. PradoAbstract:Postural instability and gait disturbances, common disabilities in the elderly and frequently present in Parkinson's disease (PD), have been suggested to be related to dysfunctional cholinergic signalling in the brainstem. We investigated how long-term loss of cholinergic signalling from mesopontine nuclei influence motor behaviours. We selectively eliminated the Vesicular Acetylcholine Transporter (VAChT) in pedunculopontine and laterodorsal tegmental nuclei cholinergic neurons to generate mice with selective mesopontine cholinergic deficiency (VAChTEn1-Cre-flox/flox). VAChTEn1-Cre-flox/flox mice did not show any gross health or neuromuscular abnormality on metabolic cages, wire-hang and grip-force tests. Young VAChTEn1-Cre-flox/flox mice (2-5 months-old) presented motor learning/coordination deficits on the rotarod; moved slower, and had smaller steps on the catwalk, but showed no difference in locomotor activity on the open field. Old VAChTEn1-Creflox/flox mice (13-16 months-old) showed more pronounced motor learning/balance deficits on the rotarod, and more pronounced balance deficits on the catwalk. Furthermore, old mutants moved faster than controls, but with similar step length. Additionally, old VAChT-deficient mice were hyperactive. These results suggest that dysfunction of cholinergic neurons from mesopontine nuclei, which is commonly seen in PD, has causal roles in motor functions. Prevention of mesopontine cholinergic failure may help to prevent/improve postural instability and falls in PD patients. This article is protected by copyright. All rights reserved.
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Deletion of the Vesicular Acetylcholine Transporter from pedunculopontine/laterodorsal tegmental neurons modifies gait.
Journal of neurochemistry, 2017Co-Authors: Helena Janickova, Marco A. M. Prado, Kaie Rosborough, Mohammed A. Al-onaizi, Ornela Kljakic, Monica S. Guzman, Robert Gros, Vânia F. PradoAbstract:Postural instability and gait disturbances, common disabilities in the elderly and frequently present in Parkinson's disease (PD), have been suggested to be related to dysfunctional cholinergic signalling in the brainstem. We investigated how long-term loss of cholinergic signalling from mesopontine nuclei influence motor behaviours. We selectively eliminated the Vesicular Acetylcholine Transporter (VAChT) in pedunculopontine and laterodorsal tegmental nuclei cholinergic neurons to generate mice with selective mesopontine cholinergic deficiency (VAChTEn1-Cre-flox/flox). VAChTEn1-Cre-flox/flox mice did not show any gross health or neuromuscular abnormality on metabolic cages, wire-hang and grip-force tests. Young VAChTEn1-Cre-flox/flox mice (2-5 months-old) presented motor learning/coordination deficits on the rotarod; moved slower, and had smaller steps on the catwalk, but showed no difference in locomotor activity on the open field. Old VAChTEn1-Creflox/flox mice (13-16 months-old) showed more pronounced motor learning/balance deficits on the rotarod, and more pronounced balance deficits on the catwalk. Furthermore, old mutants moved faster than controls, but with similar step length. Additionally, old VAChT-deficient mice were hyperactive. These results suggest that dysfunction of cholinergic neurons from mesopontine nuclei, which is commonly seen in PD, has causal roles in motor functions. Prevention of mesopontine cholinergic failure may help to prevent/improve postural instability and falls in PD patients. This article is protected by copyright. All rights reserved.
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reduced expression of the Vesicular Acetylcholine Transporter and neurotransmitter content affects synaptic vesicle distribution and shape in mouse neuromuscular junction
PLOS ONE, 2013Co-Authors: Hermann A Rodrigues, Marco A. M. Prado, Vânia F. Prado, Matheus De Castro Fonseca, Wallace L Camargo, Patricia Lima, Patricia Massara Martinelli, Ligia Araujo Naves, Cristina GuatimosimAbstract:In vertebrates, nerve muscle communication is mediated by the release of the neurotransmitter Acetylcholine packed inside synaptic vesicles by a specific Vesicular Acetylcholine Transporter (VAChT). Here we used a mouse model (VAChT KDHOM) with 70% reduction in the expression of VAChT to investigate the morphological and functional consequences of a decreased Acetylcholine uptake and release in neuromuscular synapses. Upon hypertonic stimulation, VAChT KDHOM mice presented a reduction in the amplitude and frequency of miniature endplate potentials, FM 1–43 staining intensity, total number of synaptic vesicles and altered distribution of vesicles within the synaptic terminal. In contrast, under electrical stimulation or no stimulation, VAChT KDHOM neuromuscular junctions did not differ from WT on total number of vesicles but showed altered distribution. Additionally, motor nerve terminals in VAChT KDHOM exhibited small and flattened synaptic vesicles similar to that observed in WT mice treated with vesamicol that blocks Acetylcholine uptake. Based on these results, we propose that decreased VAChT levels affect synaptic vesicle biogenesis and distribution whereas a lower ACh content affects vesicles shape.
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Regulation of cholinergic activity by the Vesicular Acetylcholine Transporter
The Biochemical journal, 2013Co-Authors: Vânia F. Prado, Robert Gros, Ashbeel Roy, Benjamin Kolisnyk, Marco A. M. PradoAbstract:Acetylcholine, the first chemical to be identified as a neurotransmitter, is packed in synaptic vesicles by the activity of VAChT (Vesicular Acetylcholine Transporter). A decrease in VAChT expression has been reported in a number of diseases, and this has consequences for the amount of Acetylcholine loaded in synaptic vesicles as well as for neurotransmitter release. Several genetically modified mice targeting the VAChT gene have been generated, providing novel models to understand how changes in VAChT affect transmitter release. A surprising finding is that most cholinergic neurons in the brain also can express a second type of Vesicular neurotransmitter Transporter that allows these neurons to secrete two distinct neurotransmitters. Thus a given neuron can use two neurotransmitters to regulate different physiological functions. In addition, recent data indicate that non-neuronal cells can also express the machinery used to synthesize and release Acetylcholine. Some of these cells rely on VAChT to secrete Acetylcholine with potential physiological consequences in the periphery. Hence novel functions for the oldest neurotransmitter known are emerging with the potential to provide new targets for the treatment of several pathological conditions.
